What is the precedence of operators in php?

Operator precedence specifies how "tightly" two expressions are bound. For example, the expression 1 5 * 3 evaluates to 16 instead of 18 because the multiplication sign ("*") has higher precedence than the plus sign (" "). Parentheses can be used to force a priority change if necessary. For example: (1 5) * 3 has the value 18.

The operator priority determines the order of operations. The one with higher operation level is calculated first. If the priorities are the same, the combination direction of the operators determines how to operate. Priority changes can be forced by using parentheses.

The order of operator precedence from high to low is as follows:

##left – .Arithmetic operators and string operatorsleft<< >>Bitwise operatorNone= = != === !== <>Comparison operatorLeft&bit operation Symbols and references left^bit operatorsleft|Bitwise operators##leftleftleftRightleftleftleftleft is used in many places to pair operators with the same precedence , the left associative direction means that the evaluation will be from left to right, and the right associative direction means vice versa. It is possible that an operator with the same precedence without associative direction cannot be combined with itself.

Combining direction	Operator	Additional information
None	clone new	clone and new
left	[	array()
right	— ~ (int) (float) (string ) (array) (object) (bool) @	Type and increment/decrement
None	instanceof	Type
Right	!	Logical operator
Left	* / %	Arithmetic operators
&&	Logical operators
||	Logical operator
? :	Ternary operation Symbol
= = -= *= /= .= %= &= |= ^= <<= >>= => ;	Assignment operator
and	Logical operator
xor	logical operator
or	logical operator
,

Example: Combining Directions

<?php 
$a = 3 * 3 % 5; // (3 * 3) % 5 = 4 
$a = true ? 0 : true ? 1 : 2; // (true ? 0 : true) ? 1 : 2 = 2 
$a = 1; 
$b = 2; 
$a = $b += 3; // $a = ($b += 3) -> $a = 5, $b = 5 
// mixing ++ and + produces undefined behavior 
$a = 1; 
echo ++$a + $a++; // may print 4 or 5 
?>

Note: Using parentheses, even when not strictly required, often enhances the readability of your code.

Although

=

has lower precedence than most other operators, PHP still allows expressions like the following: if (!$a = foo()), in this case The return value of foo() is assigned to $a.

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